Greenhouses have been developed and introduced in the Netherlands for three reasons: 1) to be able to cultivate crops that can not be cultivated in the Dutch climate, 2) to give a longer cultivation season to full land crops, 3) to be able to guarantee a more controllable quality. The conditioning of the greenhouse is essential: temperature, atmospheric humidity and CO2 concentration determine, together with the supply of light, the quality and quantity of a crop. Because of the different requirements regarding the indoor climate, per crop considerable differences in the applied fitting techniques are possible.
Basic equipment consists of the central generation of heat and CO2 by means of boilers. The heat is distributed through pipes, which also serve the internal transport system. Moisture is brought in by the crop and provides in summer for the cooling of the greenhouse, combined with the ventilation through the opening of the windows. Ventilators suspended from the greenhouse construction provide here for a better distribution of the conditions. In addition to the use of energy of the ventilators, this has also consequences for the greenhouse construction. The greenhouse construction must be carried out heavier (and thus more expensive), because it also serves as supporting construction for the ventilators and the windows to be opened.
At the moment, it is not possible to operate/control the temperature, atmospheric humidity and CO2 concentration independently from one another. Dehumidification of the greenhouse takes for example place by simply opening windows. The greenhouse is herewith not only de-moisturized, but the CO2 also disappears and the optimal greenhouse temperature gets disturbed. An additional disadvantage is the possible contamination from the surroundings (insects, diseases, etc.).
In modern greenhouse farming the “Innogrow” concept is generally known. In this concept the air is demoisturized by first cooling it and then partially heating it again. The cool, dry air is distributed by large textile hoses under the crop. A direct result is that enormous quantities of air have to be moved by means of ventilators. The length of the production line is furthermore limited, because a larger production line requires the air hose to have a larger diameter. The tendency goes towards production lines that are as long as possible. The generation of cold and heat takes place by means of heat pumps and storage of energy in the soil. It is important that the concept consists of a heat surplus and that it can only be realized by placing a conventional greenhouse adjacent to it.